JPH081803B2 - Fuel cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cell structure of a stacked fuel cell.

[Prior Art] FIG. 4 is a sectional view showing the most typical conventional cell structure disclosed in Japanese Patent Publication No. S58-152 and Japanese Patent Publication No. S59-66067, in which 1 is an electrolyte. Matrix, 2 and 3 are electrodes, 4 and 5 are electrode base materials, 6 and 7 are electrode catalyst layers, 8 and 9 are wet gas seals, and 10 is a gas separation plate (gas separation plate 10 is a separator and interconnector). , 11 and 12 are gas flow paths for fuel and oxidant gas that are orthogonal to each other.

 Next, the operation will be described.

The gas separation plate 10 is a gas-impermeable plate made of, for example, dense carbon, and has gas passages 11 and 12 formed on both sides thereof and orthogonal to each other.

On the other hand, the electrode base materials 4 and 5 are made of, for example, porous carbon fiber, and the fuel gas and the oxidant gas supplied to the gas flow paths 11 and 12 are diffused in the electrode base materials 4 and 5 and the catalyst of the electrode. It reaches the entire surface of layers 6 and 7 and reacts through the electrolyte matrix 1 to generate electricity.

Excess gas not used here for the reaction and water vapor as a reaction product are discharged to the outside through the gas flow paths 11 and 12. In this exhaust gas, the electrolyte matrix 1,
Electrolytes contained in the electrodes 2 and 3 exist as droplets or vapor determined by the operating conditions of the fuel cell, and the droplets and vaporized electrolyte are also discharged to the outside.

The infiltrating gas seals 8 and 9 prevent the fuel and the oxidant gas from leaking from the porous electrode base material to the outside.

[Problems to be Solved by the Invention] Since the conventional fuel cell is configured as described above, the electrolyte is held only by the electrolyte matrix 1, the catalyst layers 6, 7 and the wet gas seals 8, 9. Therefore, when the operation is performed for a long period of time, the electrolyte becomes insufficient due to scattering, evaporation, etc., and it is necessary to frequently replenish the electrolyte.

Further, the volume of the electrolyte changes greatly depending on the operating conditions such as the operating pressure, the operating temperature, the gas utilization rate, and the position in the cell plane.
The parts of the catalyst layers 6, 7 and the wet gas seals 8, 9 are not capable of absorbing.

In order to absorb this change in the volume of the electrolyte, an external reservoir as shown in, for example, JP-A-58-161269 may be provided, but the cell size is large and the movement distance of the electrolyte in the electrolyte matrix 1 is large. If it becomes longer, it will not be able to function sufficiently, and the expanded portion of the electrolyte will overflow into the catalyst layers 3, 4, the electrode base materials 5, 6 or the gas flow paths 11, 12, causing the battery to flood and deteriorate the battery characteristics. was there.

The present invention has been made to solve problems such as steam, and an object of the present invention is to provide a fuel cell capable of storing an excess electrolyte and absorbing a volume change of the electrolyte without flooding. And

[Means for Solving the Problems] In the fuel cell according to the present invention, a gas separation plate is arranged with a dense layer and a gas channel formed on at least one surface of the dense layer, and the pore size is set to the maximum pore size of the electrolyte matrix. It is composed of a larger porous portion, and the electrolytic solution is stored by leaving a void portion in the porous portion.

[Operation] The gas separation plate of the fuel cell according to the present invention prevents the gases flowing on both sides from being mixed by the dense layer, and the porous portion provided on at least one surface of the dense layer forms a gas flow path which is orthogonal to each other. Is supplied to the electrode, and excess pores that do not directly participate in the power generation reaction are stored by leaving pores inside the porous part, and the pore size of the porous part is larger than the maximum pores of the electrolyte matrix, so that gas is supplied to the electrode. In addition to efficiently diffusing, when the electrolyte in the electrolyte matrix is insufficient, the electrolyte is supplied and replenished so that the electrolyte matrix can be sufficiently filled from the porous portion. Also, when the electrolyte undergoes a volume change, it effectively absorbs this.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an electrolyte matrix, 6 and 7 are electrode catalyst layers, 11 and 12 are gas passages of fuel and oxidant gas which are orthogonal to each other, and 16 is a gas separation plate (referred to as a composite rib separator). Then, the dense layer 13 and the porous portions 14 and 15 formed in a rib shape on both sides thereof are integrally formed.

The pores 14 and 15 have a pore size larger than the maximum pore of the electrolyte matrix.

 Next, the operation will be described.

The fuel and the oxidant gas are supplied to the gas flow paths 11 and 12 formed by the porous portions 14 and 15 on both sides of the gas separation plate (separator with composite ribs) 16 and orthogonal to each other. At this time, the dense layer 13 of the gas separation plate 16 prevents the fuel and the oxidant gas flowing on both sides from mixing with each other, and both gases reach the electrode catalyst layers 6 and 7. The gas reaching the catalyst layer is ionized and reacted through the electrolyte matrix 1 to generate electricity.

Excess gas not used here for the reaction and water vapor as a reaction product are discharged to the outside through the gas flow paths 11 and 12. The exhaust gas contains the electrolyte contained in the electrolyte matrix 1 and the electrode catalyst layers 6 and 7 as droplets or vapor, and is discharged to the outside.

Therefore, when the operation is carried out for a long period of time, the electrolyte inside the electrolyte matrix 1 and the electrode catalyst layers 6 and 7 becomes insufficient.
The electrolyte impregnated in both and / or one of 15 compensates for the electrolyte matrix 1 and the electrocatalyst layers 6 and 7
To move the fuel cell to a stable operation for a long time.

Since the movement of the electrolyte is performed by the capillary suction force determined by the pore size of each member and the wettability with respect to the electrolyte, the pore size and the degree of water repellent treatment may be adjusted between the members.

Here, since the pore sizes of the porous parts 14 and 15 are made larger than the maximum pores of the electrolyte matrix 1, the electrolyte is insufficient in the electrolyte matrix 1, and when the electrolyte matrix 1 moves from the porous parts 14 and 15 to the electrolyte, Can be supplied and replenished sufficiently without generating an unfilled area,
It can operate stably without impairing the gas separation effect.

As mentioned above, the supplementary function of the shortage due to the scattering and evaporation of the electrolyte has been described. Especially when the electrolyte is phosphoric acid, start / stop or operating conditions (operating pressure, operating temperature, gas utilization rate, etc.) Since the volume of the electrolyte changes greatly (expansion / contraction) depending on the position within the cell surface, it is necessary to have a function of absorbing the change in the volume of the electrolyte.

Although the porous parts 14 and 15 of the gas separation plate 16 are impregnated with an electrolyte, they are assembled in a state in which pores are left, and during operation, they are expanded inside the electrolyte matrix 1 and the electrode catalyst layers 6 and 7. The formed electrolyte can be absorbed by the porous portions 14 and 15 of the gas separation plate 16 which are adjacent to each other. When the electrolyte contracts, the electrolyte moves to a necessary portion in the same manner as when the electrolyte contracts. Further, the gas diffuses into the electrode catalyst layer in contact with the porous portions through the pores in the porous portions 14 and 15 which are not impregnated with the electrolyte.

In the above-mentioned embodiment, the porous portions 14 and 15 are described as ribs, but it is not always necessary that the gas can be uniformly supplied to the electrode catalyst layer. As shown in FIG.
The porous portions may be arranged in a uniform stepping stone shape so that 11 and 12 are formed. Further, the porous portions 14 are formed on both sides of the gas separation plate 16.
Although 15 and 15 are provided, either one may be formed as a conventional dense layer as shown in FIG.

[Effects of the Invention] As described above, according to the present invention, the gas separation plate has the dense layer and the pore size of the gas passage arranged on at least one surface of the dense layer to be larger than the maximum pore of the electrolyte matrix. It is composed of a porous part, and the electrolyte is stored in a state where pores are left in the porous part, so an extra electrolyte that does not directly participate in the power generation reaction can be built in the electrode, without replenishing the electrolyte for a long time. It can operate stably. Also,
Since the volume change of the electrolyte due to the operating conditions is also efficiently absorbed by the porous portion over the entire electrode surface, no trouble such as flooding occurs. Further, the gas diffuses into the electrode catalyst layer in contact with the porous portion through the pores in the porous portion that are not impregnated with the electrolyte, so that the power generation reaction in the electrode catalyst layer can be efficiently performed on the entire surface.

[Brief description of drawings]

FIG. 1 is a sectional view showing the basic structure of a fuel cell according to an embodiment of the present invention, FIGS. 2 and 3 are sectional views showing other embodiments of the present invention, and FIG. 4 is a conventional fuel cell. It is sectional drawing which shows the basic composition of. In the figure, 1 is an electrolyte matrix, 2 and 3 are electrodes, 11 and 12 are gas flow paths, 13 is a dense layer, 14 and 15 are porous parts, and 16 is a gas separation plate. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-145066 (JP, A) JP-A-58-89780 (JP, A) JP-A-59-93358 (JP, A)

Claims (3)

[Claims] 1. A pair of electrodes sandwiching an electrolyte matrix,
In a structure in which a plurality of gas separation plates are formed on both sides of which a gas flow path is formed to flow fuel gas and oxidant gas at right angles to each other, the gas separation plate is a dense layer and at least one surface of the dense layer. The gas flow path is configured to be arranged in, and a pore portion having a pore size larger than the maximum pore of the electrolyte matrix, and a porous portion is left in the porous portion to store the electrolytic solution. A fuel cell characterized by the above. 2. The fuel cell according to claim 1, wherein the porous portion of the gas separation plate is subjected to water repellent treatment. 3. The fuel cell according to claim 1, characterized in that, in the porous portion provided on both sides of the gas separation plate, the pore size distribution is changed for each side, or one side is subjected to water repellent treatment.